This project concerns the correlation of gonodal hormone titers with differences in mating behavior; the effects of copulation on the endocrine system; and the site and mode of androgen action on male behavior. Using radioimmunoassay, to measure circulating hormone levels, we will first determine whether any features of the individual variations in patterns of mating behavior can be correlated with plasma testosterone in the male and ovarian steroids in the female. Hormone- behavior relationships will be studied during development, and the latency of effects of testosterone and progesterone on male and female sexual behavior respectively will be precisely determined. The neural pathways underlying mating-induced pituitary gonadotropin release in the female and the possible involvement of catecholamines (as neurotransmitters) and of adrenal progesterone in this "reflex" will be studied. Possible behavioral consequences of effects of mating and stress on testosterone secretion will be evaluated. The respective roles of androgenic stimulation of the brain and of the genital tissues will be evaluated in terms of their relative importance in male copulation. The hypothesis that testosterone's effect on male sexual behavior is mediated by aromatization of the androgen to estrogen will be assessed, using peripheral and intrahypothalamic implantation of various steroids.